Fetch details of banned and blocked users

Carla Dragorequested to merge
506436-fetch-banned-blocked-users into master

What does this MR do and why?

This change updates the UpdateSourceUsersService class to handle cases where source users are missing from the graphql Query.users response because they are banned or blocked.

The service now collects the ids that are missing from the response and uses the single Query.user graphql query to get the user details.

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Related to #506436 (closed)

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